My car is running OK. I have some other problem with my car where it sometimes stumbles and it is running very rich. I think I have carbon build up, need to replace the O2 sensor, or have some other issue. Boost leak may be a problem too.
My plugs did make my car run significantly better. I say go with them - I’m having other problems with my motor. My timing is significantly retarded from factory specs – someone in Japan did this on purpose. I had my shop at lunch today set it to factory timing and try and re-adjust the idle and my car was running very badly. I don’t think my problem is realted to plugs at all. Mechanic said it could be a) valve problem or carbon buildup (because of pinging and weird valve noises) or else a bottom end connecting rod bearing problem. I’m really scared now. 
Again, from everything I heard, 6 heat range plugs are great for a stock car. If you know that in the next 50-80,000 kms you will be putting on a bigger turbo or increasing your HP more than 20-30%, go with the ultra cold plugs at 7.
Just remember, that if you have a near stock car 7 plugs may actually run very badly for you. Then again, they may run better. Factory plugs that I pulled from my car were heat range 6, so I stuck with it.
Lastly, my local Can Tire and Partsource don’t stock range 7 plugs – I have to special order them. So unless you really need them, I’d stick with 6. And if you want to save money or have a bit of fun experimenting, there is nothing wrong with going with a lower grade plug. Apparently though, you should only use platinums in this car. I hear that copper is a problem for some reason, but I have no idea. I wouldn’t leave coppers in there for too long – copper has a very low melting point compared to platinum or iridium type plugs - and detonation kills copper plugs much faster than normal.
I say, stock cars should keep using 6’s and more heavily boosted cars should switch to 7’s.